Failure warning device for exhaust gas recirculation system

ABSTRACT

A detector which actuates a relay to energize an alarm in response to a inoperability of an exhaust gas recirculation system metering valve.

United States Patent Mawatari et al.

FAILURE WARNING DEVICE FOR EXHAUST GAS RECIRCULATION SYSTEM Inventors: Toshihiro Mawatari, Yokosuka;

Takashi Kunugi; Masanori Harada; Kenichi Sasaki, Yokohama, all of Japan Assignee: Nissan Motor Company, Limited,

Yokohama City, Japan Filed: Sept. 7, 1973 Appl. No.: 394,988

Foreign Application Priority Data [58] Field of Search 123/119 A, 198 D, 198 R;

[56] References Cited UNITED STATES PATENTS 3,779,222 12/1973 Lorenz 123/119 A 3,794,006 2/1974 Woodward 123/119 A OTHER PUBLICATIONS Society of Automotive Engineers Paper No. 700146, Pages 2, 3, and FIG. 2, Jan. l2-l6, 1970.

Primary ExaminerWendell E. Burns O 9 [57] ABSTRACT ct. 3, 1 72 Japan 47-1 14764 A detector which actuates a relay to energize an alarm Sept. 9, 1972 Japan 47-90636 In response to a inoperablllty of an exhaust gas reclr- US. Cl 123/119 A, 60/278, 123/198 D, culatio System metermg Valve- Int. Cl F 02m 25/06 10 Claims, 9 Drawing Figures 50 "4" 6"a 62 54 I 47 g )Q aim l L l p 8 PATENIE; :isvzslsn SHEET w 3. 3.850.151

FAILURE WARNING DEVICE FOR EXHAUST GAS RECIRCULAT-ION SYSTEM circulated through the system when needed. However,

it is quite difficult to do so becuase the exhaust gas re-' circulation installation is generally inaccesible.

It is known that exhaust gas will not recirculate if an exhaust gas flow metering valve in the recirculation conduit malfunctions due to rupture of the diaphragm and/or sticking of the valve head to the valve seat caused by corrosion or deposition of fuel additives.

It is therefore a main object of the present invention to provide a device which warns a driver if an exhaust gas recirculation system fails.

It is a further object of the present invention to provide a simple failure warning device for an exhaust gas recirculation system.

It is another object of the present invention to provide a failure warning device which can instantly check whether an exhaust gas recirculation system is operable.

These and other objects and features of the present invention will be more apparent from the following description taken together with the accompanying drawings, in which:

FIG. 1 is a schematic partial sectional view of an exhaust gas recirculation system incorporating the present invention;

FIG. 2 is a view taken along a line 11-11 of FIG. 1;

FIG. 3 is a wiring diagram of one form of a first preferred embodiment of a failure warning device according to the present invention;

FIG. 4 is a wiring diagram of another form of the embodiment of FIG. 1

FIG. 5 is a view similar to FIG. 1 and shows detector switches used in the embodiment of FIG. 4;

FIG. 6 is a view showing a modified switch arrangement of the FIG. 4 embodiment;

FIG. 7 is a view showing another switch arrangement for the FIG. 4 embodiment;

FIG. 8 is a wiring diagram of a second preferred embodiment of a failure warning device according to the present invention; and

FIG. 9 is a view similar to FIG. 1 and shows a switch used in the FIG. 8 embodiment.

Referring to the accompanying drawings and particularly to FIGS. 1 to 3, there is shown a first embodiment of the present invention.

In FIG. 1 there is shown a conventional exhaust gas recirculation system having an exhaust gas recirculation conduit 10 leading from an exhaust system of an engine (not shown) to a downstream side of a throttle valve 12 of a carburetor 14 which is provided with a venturi 16. The exhaust gas recirculation conduit 10 incorporates a metering valve 18 by which the flow of exhaust gas through the recirculation conduit 10 is metered in dependence on the vacuum in the intake system such as at the throttle valve 12. The metering valve 18 is fastened at its upper end to the center of 21 diaphragm 20. An atmospheric chamber 22 below the diaphragm is open to the ambient air and a vacuum chamber 24 above the diaphragm 20 is connected to a portion of the intake system such as to a throttle vacuum port 26 (see FIG. 2) by means of a conduit 28. A compression spring 30 biases the diaphragm 20 downward to urge the metering valve 18 toward a closed position. The above described configuration is well known in the art, and further explanation is unnecessary.

In order to detect in operability or a mulfunction of the metering valve 18, a valve opening detector such as a diaphragm switch 32 is proposed. A diaphragm 34 divides the interior of the diaphragm switch 32 into chambers 36 and 40. The chamber 36 communicates with the conduit 28 through a conduit 38, and the chamber 40 communicates with another throttle vacuum port 42 through a conduit 44 (see FIG. 2). The diaphragm switch 32 has a contact 46 mounted on the diaphragm 34, and another contact 48 mounted on a casing (no numeral) of the diaphragm switch 32 as shown in FIG. 1. The casing and the diaphragm 34 of the diaphragm switch 32 are electrically insulated from each other in a suitable manner. The contacts 46 and 48 are disposed in the diaphragm switch 32 such that they disengage when the pressures in the chambers 36 and 40 are equal, and engage when the diaphragm 34 moves beyond a predetermined position when the pressure in the chamber 36 is higher than the pressure in the chamber 40. Thus, the switch 32 is able to detect a condition in which the diaphragm 20 is ruptured, since in this case the pressure in the chamber 24 will approach atmospheric pressure.

Referring particularly to FIG. 3, there is shown a wiring diaphragm of a failure warning device embodying the invention incorporating the detector or diaphragm switch 32. One side of an electric power source 49 is connected to around and the other side to an ignition switch 50 which is closed when the engine is running. The other side of the switch 50 is connected to ground through relay contacts 52 and 54 in series with an alarm 56 such as a buzzer which produces a warning signal when a circuit is completed therethrough with the power source '49. Connected in series to ground from the junction between the switch 50 and contact 52 are a load such as a resistor and a relay 58 which operates to connect the contacts 52 and 54 when a current above a predetermined value flows through the relay 58. A fuse 62 is connected to ground from the junction between the load 60 and relay 58. The contacts 46 and 48 are connected in parallel with the load 60. The failure warning device illustrated in FIG. 3 is designed such that if the diaphragm 20 is intact, the contacts 46 and 48 will be disconnected and the alarm 56 will be de-energized. However, if the diaphragm 20 ruptures, the contacts 46 and 48 will engage, and current will flow through the switch 50, the contacts 46 and 48, and the fuse 62. This will cause the fuse 62 to blow. In this case, a high value of current will flow through the relay 58 which will energize it to connect the contacts 52 and 54 and energize the alarm 56. The alarm 56 will continue to indicate the warning condition as long as the switch 50 is closed. The device is reset by replacing the fuse 62 after repairing the diaphragm 20. If desired, the fuse 62 may be a resettable circuit breaker. The load 60 is selected so that when the contacts 46 and 48 are disconnected, the current flow through the switch 50, load 60 and fuse 62 is insufficient to blow the fuse 62. However, when the contacts 46 and 48 are connected, the fuse 62 is connected to the source 49 through a lowresistance path, the current increases, and the fuse 62 blows. As long as the fuse 62 is intact, the relay S8 is de-energized because it is effectively shunted to around through the fuse 62. However, when the fuse 62 blows, the shunt is removed and the relay 58 is energized. It will be noticed that the relay 58 will remain energized even if the contacts 46 and 48 are disconnected due to the parallel connection of the load 60 and contacts 46 and 48 because sufficient current will flow through the load 60 to energize the relay 58.

Referring to FIG. 4, there is shown a modified form of a failure warning device embodying the invention. This failure warning device is similar to that of FIG. 3 except that three switches 64, 66 and 68 connected in series are employed instead of the single switch 32. Thus the same reference numerals are used for like elements.

Referring now to FIGS. 4 and inclusive, the switch 64 is a conventional engine temperature sensing switch which closes when the engine temperature is above a first predetermined value and opens when the engine temperature is below the first predetermined value. The switch 66 is an intake vacuum sensing switch which has a diaphragm 70, an atmospheric chamber 72, a vacuum chamber 74 connected to the conduit 28 by a conduit 76, and a set of contacts (no numeral) which are disengaged when the vacuum in the chamber 74 is lower than a second predetermined valvett and are engaged when the vacuum is higher than the second predetermined value. The second predetermined vacuum value is preferably -50 mmHg for the vacuum switch66 although any vacuum value between 50 mmHg and 400 mmHg may be selected.

The switch 68 is a valve opening sensing switch which is closed when the metering valve 18 is not open to a third predetermined value and opened when the valve opening exceeds the third predetermined value. Preferably, this third predetermined value is selected so that contacts 78 and 80 of the switch 68 are disengaged when the vacuum is higher than -45 mmHg and engaged when the vacuum is lower than 45 mmHg. The third predetermined value is expressed in terms of intake vacuum producing the corresponding valve opening degree under normal system operating conditions.

It is to be noted that the engine temperature sensing switch 64 and the intake vacuum sensing switch 66 are open under conditions in which recirculation of exhaust gas is not required, such as when the engine is cold and/or when the intake vacuum is low, and closed when recirculation of exhaust gas is required.

It will thus be understood that if the metering valve 18 fails to operate under conditions in which recirculation of exhaust gas is required, all the switches 64, 66 and 68 will close and a warning signal will be produced by the alarm 56.

FIG. 6 illustrates a modified form of the vacuum sensing switch 66 of FIG. 5. A modified intake vacuum sensing switch 66' differs from that of FIG. 5 in that a vacuum chamber 74 is connected to a spark advance vacuum port 82 of the carburetor 14. The intake vacuum sensing switch 66 is advantageous over the switch With the valve opening switch 68, it can not be detected if the valve seat of the metering valve 18 is clogged and no recirculation of exhaust gas is provided because the valve 18 may be open. If the valve seat of the metering valve 18 is clogged, exhaust gas does not flow through the conduit 10 and the temperature therein downstream of the valve 18 will be low. To detect this condition, a temperature sensing switch 84 having a bimetallic element, thermistor or thermocouple may be employed in the conduit 10 downstream of the valve 18 as shown in FIG. 7 instead of the valve opening sensing switch 68. The temperature sensing switch 84 is designed to close when the temperature downstream of the valve 18 in the recirculation conduit 10 is below a fourth predetermined value, such as below 100C or 200C, and open when the temperature is above the fourth predetermined value.

Referring next to FIGS. 8 and 9 inclusive, there is shown another preferred embodiment of a failure warning device according to the present invention. In this embodiment, an alann is energized when the ignition switch is closed and remains energized until the exhaust gas recirculation system (metering valve) begins to operate. The failure warning device illustrated in FIG. 8 has an electric power source 86, an ignition switch 88, a set of normally closed contacts and 92 of a latching type relay 96, and an alarm 94 such as a lamp. The electric power source 86, the ignition switch 88, the set of normally closed contacts 90 and 92 and the alarm 94 are connected in series as shown. The

. relay 96 of the failure warning device may be an electromagnetic re relay or an electronic relay employing switching transistors. An electromagnetic relay 96 as shown has a solenoid coil 98 and a set of normally open contacts 100 and 102. The coil 98 and the normally open contacts 100 and 102 are connected in seies with the ignition switch 88 as shown. The failure warning device further has a detector such as a valve opening sensing switch 104 connected in parallel with the normally open contacts 100 and 102 of the relay 96 as shown. If the siwtch 104 is closed due to failure of the valve 18, the relay 96 will energize and latch to energize the alarm 94. The alarm 94 will remain energized even if the switch 104 is subsequently opened as long as the ignition switch 88 is closed.

Referring particularly to FIG. 9 there is shown a de tailed configuration of the metering valve 18 and diaphragm 20 incorporating the valve opening switch 104. As shown, the diaphragm 20 is clamped between an uppercasing 106 and a lower casing 108, and the compression spring 30 biases the diaphragm 20 downward through a washer 110.

The valve opening switch 104 is different from the valve opening switch 68 illustrated in FIG. 5 in that the former is closed when the metering valve 18 is open above a fifth predetermined value. One contact 112 is in the form of a ball section of a valve stem 19 of the metering valve 18, and another contact 114 is a metal leaf connected through a suitable insulator 116 to the lower casing 108. The contact 112 is grounded to the body of vehicle (not shown) through the valve stem 19, washer 110, compression spring and upper and lower casing 106 and 108. The contacts 112 and 114 engage when the metering valve 18 is open (the position of FIG. 9) and disengage when the metering valve 18 is closed.

When the ignition switch 88 is closed to start the engine and the engine is idling, the contacts 112 and 114 are disengaged because the metering valve 18 is closed, and the alarm 94 is energized. When the metering valve 18 opens as the intake vacuum increases, the contacts 112 and 114 engage to energize the coil 98, thereby causing the contacts 100 and 102 to engage while the contacts 90 and 92 disengage. Thus, the alarm 94 is de energized. If the contacts 1 12 and 1 14 once engage, the coil 98 is energized and the relay 96 electrically latches the contacts 100 and 102 together. Thus, the alarm 94 will remain energized until the ignition switch 88 is opened. Therefore, even if the metering valve 18 closes when the intake vacuum is low (such as when the engine is idling or running at full throttle), the alarm 94 remains de-energized. When the ignition switch 88 is opened to stop the engine, the coil 98 is de-energized and the failure warning device will return to the condition shown in FIG. 8.

Should the metering valve 18 fail to open, the contacts 112 and 114 will remained disengaged even if the intake vacuum increases, and the alarm 94 wil remained energized once the ignition switch 88 has been switched on. Thus, the driver will notice the failure of the exhuast gas recirculation system.

It will be appreciated that the failure warning device illustrated in FIGS. 8 and 9 inclusive can be used as a tester to determined whether or not the exhaust gas recirculation system is operable by depressing the gas pedal to increase the intake vacuum before running.

From the foregoing description with regard to the various embodiments of the present invention, it will be noted that the switch 32, the combination of switches 64, 66 and 68 and the switch 104 serve as detectors for the failure warning devices of FIGS. 3, 4 and 8, respectively.

It will now be appreciated that a failure warning device provided in accordance with the present invention is very simple in construction and very reliable in oper ation.

What is claimed is:

1. A failure warning device for an exhaust gas recirculation system for an internal combustion engine, the exhaust gas recirculation system having an exhaust gas recirculation conduit, an intake vacuum actuated metering valve to meter exhaust gas flow through the recirculation conduit, the metering valve having a diaphragm, one side of which communicates through a conduit with the engine intake system and the other side of which communicates with the atmosphere, said device comprising: an ignition switch which is closed when the internal combustion engine is operating; an alarm; a relay; and a detector to detect inoperability of said metering valve; said relay being actuated by said detector to energize said alarm in response to inoperability of said metering valve if said ignition switch is closed.

2. A device as claimed in claim 1, wherein said relay once actuated by said detector maintains said alarm energized until said ignition switch is opened.

3. A device as claimed in claim 2, wherein said detector is a valve opening sensing switch having a diaphragm, one side of which communicates with said conduit and the other side of which communicates with the intake system independently of said conduit, and a set of contacts which open and close in response to the position of said diaphragm of said valve opening sensing switch.

4. A device as claimed in claim 2, wherein said detector comprises first, second and third switches connected in series with one another, said first switch being an engine temperature sensing switch which is closed when the engine temperature exceeds a first predetermined value, said second switch being an intake vacuum sensing switch which is closed when the sensed intake system vacuum exceeds a second predetermined level, said third switch being a valve opening sensing switch which is closed when the degree of opening of said metering valve is below a third predetermined level.

5. A device as claimed in claim 4, wherein said intake vacuum sensing switch has a diaphragm, one side of which communicates with the conduit and the other side of which communicates with the atmosphere, and a set of contacts which open and close in response to the position of said diaphragm of said intake vacuum sensing switch.

6. A device as claimed in claim 4, wherein said intake vacuum sensing switch has a diaphragm, one side of which communicates with a spark advance vacuum port of the intake system and the other side of which communicates with the atmosphere, and a set of contacts which open and close in response to the position of said diaphragm of said throttle vacuum sensing switch.

7. A device as claimed in claim 2, wherein said detector has first, second and third switches connected in series with one another, said first switch being an engine temperature sensing switch which is closed when the engine temperature exceeds a first predetermined value, said second switch being an intake vacuum sensing switch which is closed when the sensed intake system vacuum exceeds a second predetermined value, said third switch being a temperature sensing switch which is closed when the temperature in the recirculation conduit downstream of the metering valve is below a fourth predetermined value.

8. A device as claimed in claim 1, wherein the detector actuates said relay to de-energize said alarm once said metering valve operates.

9. A device as claimed in claim 8, wherein the detector is a switch which closes when the opening degree of said metering valve is above a fifth predetermined value.

10. A device as claimed in claim 9, wherein the relay is a latching type relay which maintains said alarm deenergized once said metering valve operates. 

1. A failure warning device for an exhaust gas recirculation system for an internal combustion engine, the exhaust gas recirculation system having an exhaust gas recirculation conduit, an intake vacuum actuated metering valve to meter exhaust gas flow through the recirculation conduit, the metering valve having a diaphragm, one side of which communicates through a conduit with the engine intake system and the other side of which communicates with the atmosphere, said device comprising: an ignition switch which is closed when the internal combustion engine is operating; an alarm; a relay; and a detector to detect inoperability of said metering valve; said relay being actuated by said detector to energize said alarm in response to inoperability of said metering valve if said ignition switch is closed.
 2. A device as claimed in claim 1, wherein said relay once actuated by said detector maintains said alarm energized until said ignition switch is opened.
 3. A device as claimed in claim 2, wherein said detector is a valve opening sensing switch having a diaphragm, one side of which communicates with said conduit and the other side of which communicates with the intake system independently of said conduit, and a set of contacts which open and close in response to the position of said diaphragm of said valve opening sensing switch.
 4. A device as claimed in claim 2, wherein said detector comprises first, second and third switches connected in series with one another, said first switch being an engine temperature sensing switch which is closed when the engine temperature exceeds a first predetermined value, said second switch being an intake vacuum sensing switch which is closed when the sensed intake system vacuum exceeds a second predetermined level, said third switch being a valve opening sensing switch which is closed when the degree of opening of said metering valve is below a third predetermined level.
 5. A device as claimed in claim 4, wherein said intake vacuum sensing switch has a diaphragm, one side of which communicates with the conduit and the other side of which communicates with the atmosphere, and a set of contacts which open and close in response to the position of said diaphragm of said intake vacuum sensing switch.
 6. A device as claimed in claim 4, wherein said intake vacuum sensing switch has a diaphragm, one side of which communicates with a spark advance vacuum port of the intake system and the other side of which communicates with the atmosphere, and a set of contacts which open and close in response to the position of said diaphragm of said throttle vacuum sensing switch.
 7. A device as claimed in claim 2, wherein said detector has first, second and third switches connected in series with one another, said first switch being an engine temperature sensing switch which is closed when the engine temperature exceeds a first predetermined value, said second switch being an intake vacuum sensing switch which is closed when the sensed intake system vacuum exceeds a second predetermined value, said third sWitch being a temperature sensing switch which is closed when the temperature in the recirculation conduit downstream of the metering valve is below a fourth predetermined value.
 8. A device as claimed in claim 1, wherein the detector actuates said relay to de-energize said alarm once said metering valve operates.
 9. A device as claimed in claim 8, wherein the detector is a switch which closes when the opening degree of said metering valve is above a fifth predetermined value.
 10. A device as claimed in claim 9, wherein the relay is a latching type relay which maintains said alarm de-energized once said metering valve operates. 